(Bloomberg) – The Nigerian government’s military crackdown against the theft of crude in the Niger River delta has left more than a 1,000 makeshift refineries in flames, worsening pollution in the area, authorities said.

A military taskforce deployed last year to stop theft and protect facilities in Africa’s top oil producer has destroyed 1,819 makeshift refineries, set ablaze 861 boats carrying as much as 20,000 liters (5,277 gallons) each of illegally refined crude and 51 tanker trucks, force commander Major General Bata Debiro said yesterday at a conference on crude theft in Lagos.

The military’s actions also contributed to pollution in the delta, Nigerian Maritime Safety Agency Director-General Ziakede Patrick Akpobolokemi told the meeting. “Security operatives blowing up things is causing more pollution,” he said.

Security forces have been struggling to halt oil theft in the West African nation that depends on crude exports for 80 percent of government revenue and 95 percent of its export income. Authorities say more than 400,000 barrels of oil are stolen every day. Nigeria pumped about 1.9 million barrels a day last month, according to data compiled by Bloomberg.

Debiro’s 6,102 soldiers and police are operating in a 70,000 square-kilometer (27,027 square-mile) region of land, mangroves and creeks that is filled with pipelines. That area is bigger than the U.S. state of West Virginia.

Royal Dutch Shell Plc (RDSA), Exxon Mobil Corp. (XOM), Chevron Corp. (CVX), Total SA (FP) and Eni SpA (ENI) run joint ventures with state-owned Nigerian National Petroleum Corp. that pump more than 90 percent of the output of Africa’s top oil producer. They blame sabotage for most of the spills.

Illegal refiners are also to blame, officials said. To refine the oil, gangs boil the crude in open cauldrons, a process that often results in burning down large patches of the delta’s mangrove and rain forests and polluting its rivers.

The fuel they produce is sold at filling stations in the region, where legal gasoline is often sold at two to three times the normal price, said Chief of Naval Staff Vice-Admiral Dele Joseph Ezeoba.

In just one area, Ogoniland, the United Nations Environmental Programme estimated in 2011 that it would take as many as 30 years to clean up the region of 1,000 square kilometers. The report blamed spills on sabotage and the lack of pipeline maintenance by oil companies.

A Dutch District Court in The Hague ruled on Jan. 30 that Shell must pay compensation in one of five claims by Nigerian villagers from the Niger delta for a spill from its facility that affected their livelihood. Judge Henk Wien said Shell wasn’t liable for four other claims.

The UNEP report called on the Nigerian government and the nation’s oil industry to set up a $1 billion fund to clean up Ogoniland that has suffered years of pollution.

“Two years after the report UNEP report, nothing has been done about Ogoniland,” said Nnimmo Bassey, the coordinator of Oil Watch International, based in Benin City, Nigeria